RFID reader Amplifier
the operating frequency of the reader is 13.56MHz and the modulation is
Ampitude Shift Keying (ASK). i've been researching for almost a month
and i cant find the appropriate amplifier, nor a clear computation or
circuit that is when using transistors.
Another problem i have is that...is it ok to use a power amplifier and not
an RF power amplifer to do amplify the output signal of the RFID reader?
i can't find a transistor that operates at the HF band...common RF transistors are labeled for VHF and UHF only.
I also tried to implement RF op amp but i don't know to implement it
correctly and i can't find the correct amplifier that can amplify a voltage to
a higher voltage (for instance 20V) or to a higher power (4W)
Hoping for your help, thank you in advance
It must be RF power amplifier . As far as 10 and 100 %
ASK both used it should be mode a-b amplifier .
VHF transistors must be OK if are not speciall pupose .
so VHF transistors can be use to amplify signals in the HF band, even 13.56MHz?
where can i find a good tutorial notes about designing RF power amplifer? i have read and downloaded lots of documents but none of them seems to explain things very clearly.
THANK YOU!
Some general-purpose transistor can have the fT up to 1GHz. I can't locate your problem, is you need a LNA or power amplifier?
Basically, 13.56 MHz is really quite low frequency and many transitors can do the job at such low frequency, so I don't think will have any problem to select the transistors for designing the ampliifers.
For ASK, again there are many books describing the techniques to demodulate the signal at the receiver. There are basically two techniques, i.e. coherent and incoherent demodulation. For coherent demodulation, you need a carrier recovcery loop to recover the carrier which is then used for demodulation. However, this may not be usful in mobile channels such as in the RFID systems. So incoherent demodulation should be used. In this case, the receiver is much more easy to design and implement. Here you can use an envelop detector to detect the signal. The implementation is simple, however, the penalty is lower signal to noise ratio which translate into a shorter distance or range. Here you can use an envelop detector to detect the signal.
For the power amplifier used at the reader, this should not be such a problem because the power is not that high. Since the transmitted signal is simply CW, you can afford using a high efficient class-C amplifier.
You may try ad8614
Hello,
The most efficient amplifier for 13.56 MHz is a Class E amplifier.
I think you only need to transmit ASK.
For example you can use the IRF510/IRL510 transistor for that and easily get up to and more than 20W at 13.56 MHz.
There are many reference designs for that amplifier.
For example just search for Microchip MCRF45X REFERENCE DESIGN.
They use an IRL510 which has a lower threshold voltage than IRF510 so you can directly drive it with TTL inverter.
hi,
anyone able to tell if we are able to judge the power amplifier performance by looking at the Vout/Vin?
any valid links for the IRF510 as a class e power amplifier?
Thanks in advance.
Please bear in mind the RFID is bidirectional. If you simply pump as much power as possible into the antenna you are not going to increase the range. You still have to deal with the modulated load current on the antenna to tell what information the RFID transponder is sending back.
Brian.